| ( | 10 | − | x | ) | × | 20 | = | ( | 15 | − | x | ) | × | 10 |
| Left side of the equation = | 10 | × | 20 | − | x | × | 20 |
| = | 200 | − | x | × | 20 |
| 200 | − | 20 | x | = | ( | 15 | − | x | ) | × | 10 |
| Right side of the equation = | 15 | × | 10 | − | x | × | 10 |
| = | 150 | − | x | × | 10 |
| 200 | − | 20 | x | = | 150 | − | 10 | x |
| - | 20 | x | + | 10 | x | = | 150 | − | 200 |
| - | 10 | x | = | 150 | − | 200 |
| - | 10 | x | = | - | 50 |
| 50 | = | 10 | x |
| 10 | x | = | 50 |
| x | = | 50 | ÷ | 10 |
| = | 50 | × | 1 10 |
| = | 5 | × | 1 |
| x | = | 5 |